Generally, an exhaust heat recovery system is a system which may supply heating or hot water by recycling exhaust heat which is generally discharged and discarded from exhaust heat sources, such as exhaust heat from a polymer electrolyte membrane fuel cell (PEMFC), exhaust heat from an internal combustion engine (ICE), surplus heat, waste incinerating heat, drainage heat, and heat generation of a substation.
For example, the polymer electrolyte membrane fuel cell (PEMFC) which is an environmentally-friendly power generation system which directly converts chemical energy generated from oxidation into electric energy generates a large amount of exhaust heat used as cooling water during an operation of the system. However, the PEMFC generally discharges the exhaust heat to the outside through an exhaust port almost without using the exhaust heat and therefore has not actively used heat discharged as the exhaust heat from the system.
Therefore, an exhaust heat recovery system capable of easily recovering and recycling exhaust heat generated from a fuel cell system while using the existing boiler apparatus already installed in the home, etc., as it is has been developed.
As illustrated in FIG. 1, the existing exhaust heat recovery system 10 primarily heats water stored in a hot water tank 11 using an exhaust heat exchanger 11-1 of an exhaust heat source 1 and secondarily heats the primarily heated water using a boiler 12 if necessary to supply heating and hot water to a user, and as a result, may obtain an effect of more saving energy than a boiler directly using direct water having a relatively lower temperature.
In detail, the existing exhaust heat recovery system 10 uses the hot water of the hot water tank 11 as it is if the temperature of the hot water tank 11 is higher than a hot water setting temperature of the boiler 12 and additionally operates the boiler 12 to satisfy the hot water setting temperature if the temperature of the hot water tank 11 is low, when the user uses the hot water.
Further, a heat exchanger 15-1 is disposed between the generating part circuit including the exhaust heat source 1, an exhaust heat pump 15-5, etc., and the exhaust heat recovery system 10 circuit including the hot water tank 11, an expansion tank 15-2, an exhaust heat pump 15-4, an automatic supplement valve 15-3, etc., to exchange heat heated by the generating part circuit with the exhaust heat recovery system 10 and allow pumps of each circuit to control the exhaust heat recovery temperature.
However, the circuit for allowing the heat heated by the power with the exhaust heat recovery system 10 in the middle is complicated, and as a result there is a problem of control difficulty and an increase in manufacturing costs.